1. Field of the Invention
This invention relates to chromatographic columns for use in fluid phase separation processes; more particularly to an improved lower sealing means for such columns.
2. Description of the Prior Art
Chromatographic columns have long been used in the laboratory analysis of fluids. One particular type of chromatographic column is a disposable column used for separating compounds such as drugs from aqueous samples such as blood, urine, etc. The separation is accomplished by contacting a stationary phase, preferably spread over a large surface area, with a mobile phase to selectively dissolve compounds into the mobile phase and leave other compounds behind dissolved in the stationary phase. In the case of drug separation from blood or urine, the stationary phase is aqueous and is spread out on an adsorbent material packed into the column and the mobile phase is an immiscible organic solvent introduced into the inlet of the column for percolation through the packing material.
Disposable columns of the type just described have a phase separation membrane positioned beneath the packing material to permit passage of the mobile phase through the outlet of the column but to prevent passage of the stationary phase therethrough. It is crucial to the successful operation of the separation process that the phase separation membrane be sealed at its edges; otherwise, the stationary phase material can bypass the membrane and contaminate the mobile phase removed from the column as intended. The absence of proper sealing of the phase separation membrane results in what is known in the art as a "leaker".
A variety of sealing means for use as the lower seal in disposable phase-separation columns have been proposed, some of greater complexity than others. Yet an important factor to the commercial success of such disposable columns seems to have been overlooked; namely, the speed at which such columns may be assembled during the manufacturing process. If an effective sealing means requires time consuming operations for the construction and proper positioning of the seal within the column, the overall cost of the column becomes prohibitive as a disposable item.